So I am using an code and trying to communicate to another device using a usart. i have noticed that i must connect the transmit line of the usart to the transmit line of my rs232 level shifter to get things to display on my computer, why is this?
thank you.
If you are into microcontrollers, some of them has built in TX/RCV for RS232. no need for level shiftars. RS485 is better becoauz you do not need the -12V for a logic 1.
total gobbelygook 1) there are (as far as I know) no '51s with built in RS232 transcievers, if some exist I would liketo know. 2) there has not been a need for -12 to drive -232 for AGES, the MAX232 family has been around for a loooong time.
Erik
Is that true? You should connect + and - 12v. to the chip then, or are there switchers inside like in the Maxim 242 chips? Are you think on this?:
I haven't seen one with a built-in transceiver.
It is a bit problematic since you use a different technology when you design a microcontroller than you use for a transceiver since one is optimized for high speed and low power with digital signals, while another is optimized for high voltages and good tolerance to ESD and other abuse.
But jsut as Erik noted: Todays traceiver solutions normally generates their own voltages, to allow them to be fed from a single 3.3V or 5V power source.
Well, I've never seen a microcontroller with built-in RS232 transceivers!